1. Field of the Invention
This invention relates generally to the formation of a preform and the attachment thereof to a metal workpiece; and, more particularly, this invention relates to the formation and attachment of an adhesive preform to a metal workpiece.
2. Background Information
The present invention has particular utility in attaching an adhesive layer to a metal workpiece which may used as a component for metal electronic packages. Such packages are shown and disclosed in U.S. Pat. No. 4,897,508.
In one form of a metal electronic package such as disclosed in the above-mentioned patent, the package comprises two parts, a base component and a cover or lid component. The base component is generally flat, without sidewalls, and a leadframe is spaced from the base component by a sealant such as an epoxy so it is in a plane which is in alignment with the upper surface or bonding face of the electronic device which is attached to the base member. The wire bonds connecting the bonding face of the metal package and the leadframe may flex upwardly so the upper component or lid of the package includes a cavity in its interior surface to provide the space for the flexing while minimizing overall thickness of the package. A sealant, such as an epoxy, is positioned between the upper surface of the leadframe and the cover or lid component.
In practice, it has been common for the epoxy sealant to be preformed and then positioned onto the cover or base member by hand. However, not only is a hand assembly slow, but also proper placement on the cover or lid is important so that excess adhesive is not squeezed out from the edges of the package or into the internal cavity of the package.